1. Field of the Invention
The present invention relates to a lamp unit.
2. Description of the Related Art
A related lamp unit employing a luminous element such as LED and the like has been so constructed that the luminous element is mounted on a substrate, a lens is arranged at a light emitting side of the luminous element, the lens and substrate are covered by a housing and the lens is exposed from an opening (see Patent Document 1).
Patent Document 1: JP-A-2007-35788
In the related lamp unit, since there is concern about an invasion of foreign substances such as dust and the like into the housing through the opening, there has been a problem that the foreign substances are attached to a rear face side of the lens or the luminous element thereby lowering intensity of illumination, or a problem that the foreign substances attached to the rear face side of the lens or the luminous element are viewed from the outside thereof thereby lowering appearance quality thereof.
Particularly, such problems frequently appear in a lamp unit which is used as a map lamp installed on a roof portion (ceiling portion) of a vehicle interior because the foreign substances easily invade the housing through the opening of the housing.